Grower-Shippers, as the name implies, are grower's that participate in the marketing of their products. Product is harvested and usually taken to a warehouse or packing facility run by the grower-shipper. Lot based inventory control is critical to partner accounting and good management of this kind of operation. If a packing operation is undertaken, inventory can have multiple stages.
Wholesalers typically concentrate produce from many sources into strategically placed warehouses. The idea is to make many products available from single points which are conveniently located. These products are then sold in relatively small quantities to food service companies and various retailers.